A bad year for mystery short-stories? So it seems, with a weaker batch than usual from England (see Harris, above) and this odd gathering of 13 from veteran editor Hoch. Ruth Rendell's ""The New Girl Friend,"" though the Edgar Award-winner, is especially disappointing--a thin, crude, 1950s-ish slice of sexual psychopathology, far less subtle or convincing than Rendell's other kinkily motivated crimes. And while this psychosexual trend is also reflected in Dorothy Salisbury Davis' very strange ""Natural Causes"" and Joseph Hansen's heavyhanded ""The Anderson Boy,"" preachiness and sentimentality are even more serious drawbacks in the collection: Michael Collins' ""The Oldest Killer"" is a shrill polemic against the ruthless dabblings of the FBI; Clark Howard's ""Custer's Ghost"" brings together, 50 years after the last stand, a Sioux and a US soldier who exorcise all hatred; Janwillem Van de Wetering offers an ecological fable; Stanley Ellin's ""Mrs. Mouse""--after a promising start--becomes no more nor less than domestic soap-opera. And the remainder is decently tricky stuff at best (a Bernard Rhodenbarr drollery from Lawrence Block, a locked-room-at-the-zoo from Bill Pronzini), with highly predictable pieces from Stephen Wasylyk and editor Hoch himself. More varied than this year's John Creasey collection, but more humorless and irritating too: one of the least ""Best"" of all.